I have a lambda function that accesses my Postgres db in RDS via VPC. After it queries the db, I want to post a notification to SNS. Because my lambda function exists in my VPC, it cannot access SNS. I have an internet gateway on my VPC. I read through the VPC endpoint documentation and currently only s3 is supported.
Is there anyway to publish to SNS in a lambda function in a VPC?
You will need a NAT server running in your VPC to route traffic outside of the VPC. AWS now offers a managed NAT service that makes this easier.
UPDATE
As of April 2018, SNS supports VPC Endpoints via AWS PrivateLink. So, there will be no need to set up an Internet Gateway or a NAT instance in order for a Lambda function inside your VPC to publish SNS notifications.
See this blog post for more details.
I know this is old, but here's another option that works, for those who don't want to configure a NAT. Instead of trying to have a lambda function inside the VPC that interacts with SNS, split into 2 lambda functions, as follows.
Function 1 sits inside the VPC and interacts with the database, returning the result of your database interaction (eg, a list of IDs matching some criteria).
Function 2 sits outside the VPC, invokes Function 1, then processes the array of values and publishes the appropriate SNS notifications (eg, sends a message based on each ID in the list).
Would be nice if there was a VPC endpoint for SNS, but still in late 2016 this does not seem to be the case.
I finally managed to get it working...
The trick is that you MUST have 2 subnets.
A public one, with a routing table that sends traffic to the Internet Gateway of your VPC. Put the NAT in there.
And a private one, with a routing table that sends traffic to the NAT. Put the Lambdas in there. (BTW Making a public subnet means setting the Auto-assign Public IP option to Yes.)
It is outlined in this overview diagram from the AWS docs:
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Scenario2.html#Configuration-2
来源：https://stackoverflow.com/questions/35999181/how-to-let-aws-lambda-in-a-vpc-to-publish-sns-notification